Electric horn



B. AMES.

ELECTRIC HORN.

Y APPLICATION FILED MAR. 14. 1917.

PatentedSept. 7, 1920.

WVEA/ ram J0 TL ER/MES the casing.

UNITED STATES BUTLER AMES, 0]? LOWELL, MASSACHUSETTS.

ELECTRIC norm.

Specification of Letters Patent.

Patented Sept. 7, 1920.

Application filed March 14, 1917. Serial No. 154,867.

To all whom/it may concern:

Be it known that I, BUTLER AMEs, a citizen of the United States, and resident of Lowell, in the county of Middlesex and State of Massachusetts, have invented new and useful Improvements in Electric Horns, of which the following is a specification.

This invention relates to magnetic apparatus and more particularly to an electric horn having a vibratory diaphragm adapted to be actuated by an electromagnet.

Apparatus of the general character herein disclosed has been extensively used for a considerable period of time but in a form possessing certain disadvantages. For example, it has been the practice to regulate the length of the-air gap between the electromagnet and the armature on the diaphragm by adjusting the armature relatively to the diaphragm. In order to effect such an adjustment the adjusting means must be mounted on the diaphragm and this is usually objectionable for several reasons, one of which is that it unduly increases the natural period of vibration of the diaphragm. Moreover, in order to produce apparatus having the pole face or faces and the opposing face of the armature substantially parallel, as is desirable for well-known reasons, it has been necessary to form the core laminations precisely and to assemble the apparatus accurately; and this has involved excessive costs of production.

The principal objects of my invention are to .provide means for readily adjusting the magnetic means relatively to the armature,

thereby eliminating the need of armature adjusting means, for permitting movement of the magnetic means relatively to the armature so as automatically to adjust the magnetic means relatively to the armature, and for mountin the magnetic means in a simple and effective manner.

Other objects of the invention will be apparent from the following description and the accompanying drawings, in which' Figure l is a side elevation of one embodiment of the invention;

Fig. 2 is a vertical longitudinal section through the apparatus shown in Fig. 1;

Fig. 3 is a front elevation of the apparatus with the horn and diaphragm removed; and Fig. 4 is a rear elevation of the magnet and associated parts removed from The illustrated embodiment comprises a horn 1 mounted on the forward end of the casing 2, a diaphragm 3 mounted between the horn 1 and casing 2 by suitable means such as bolts 4 and an electromagnet 6 mounted within the casing to actuate the diaphragm. The casing 2 is preferably cupshaped andby this I mean a shape resembling a cup in that one end is closed, either by a member integral with-the side walls or by a member secured to the side walls, and the other end is open, the side walls either being conical or cylindrical or having any other suitable. contour.

The electromagnet 6 has a core 7 which is preferably U-shaped and which is so positioned within the casing that its two pole faces lie in juxtaposition to the armature 9 which is rigidly or fixedly mounted on the diaphragm 3 by suitable means such as the rivet 10. On either arm of the U-shaped core 7 are mounted coils 8 for energizing the core 7, these coils usually being connected in series and connected to the binding posts 11 and 12 to which a suitable source of current may be connected.

The magnetic core 7 is preferably made of laminations as shown in Fig. 3 and these laminations are held together by means of rivets 13. Members 14 and 16 of hard insulation material or other suitable material are fitted over the two arms of the U-shaped core one on either side of the field coils 8 and these members serve the double function of holding the coils 8 in position and assisting in holding the laminations together.

My preferred means for simply and adjustably mounting the electromagnet upon the casing is constructed and arranged as follows: At the rearward end of the core 7 is provided a transverse slot 17 this slot having overhanging sides 18, and a member 19 having a head 21 adapted to fit into the slot 17 is provided. The member 19 is preferably-in the form of'a machine screw adapt- .ed to be threaded into an internally threaded boss 22 projecting centrally from the rear of the cupape casing, a lock nut 23 being provided to lock the screw in osition. By adjusting the screw longitudinally in the boss 22 the electromagnet may be adjusted forwardly and rearwardly in such manner as to regulate the length of the air-gap between the pole' faces of the core 7 and the armature 9.

I have found that a device of this character when made by the ordinary rapid processes of manufacture cannot be constructed in such manner that the pole faces of the core '7 lie accurately in a plane parallel'to the opposing face of the armature 9 and for this reason I have provided means for automatically adjusting the core 7 so that the pole faces will lie in parallelism with the op posing face of the armature 9, this means preferably being substantially as follows: The transverse slot 17 in the rearward end of the core 7 is made slightly deeper than the thickness of the head 21 of screw 19 as shown in exaggerated form in Fig. 2. By virtue of this construction the electromagnet may be slightly orientated in any direction of the diaphragm carry the armature 9 against the pole faces of the core 7. In the event that the pole pieces are in parallelism with the opposing face of the armature 9, the impact of the armature is distributed uniformly over the pole faces. However, if the electromagnet is not in accurate alinement with the armature due to lack of precision of manufacture or to inaccurate assembly of the parts, or to a flexure of the bottom of the cup-shaped casing, the armature does not engage the pole faces uniformly but engages the corner or heads or portion which projects forwardly the farthest. This impact tends to orientate the elecv tromagnet about the screw head into such position that the impact is delivered substantially uniformly throughout the pole faces. In this position the electromagnet remains during vibration of the armature, especially when the rate of vibration is comparatively high.

'While it is to be understood that the screw head 21 may, if desired, fit snugly within the slot 17, the preferred form of construction is that above described, and when employing either form of construction suitable means is preferably provided to prevent rotation of the electro-magnet about its longitudinal axis. The preferred form of this means is illustrated in Fig. 2 and comprises a fiat disk of relatively hard insulating material 24, this member being fitted around the rectangular rearward end of the core 7. The member 24 is either loosely or rigidly secured to the casing 2 at a substantially radial distance from the axis of the eletromagnet and suitable means for this purpose comprise binding posts 11 and 12 passing through openings in the bottom of the easing thereby preventing rotation of the member 24 and electromagnet 6. When the binding posts are arranged tightly to secure the member 24 to the casing the automatic angular adjustment of the electromagnet about the head 21 may be permitted either by forming member 24 of material which is more or less flexible and fitting the member comparatively tightly around the core 7, or the member 24 may be made of relatively stiff material and be loosely fitted around the core, the core being prevented from r0- tating in the latter event by virtue of the rectangular cross-section of the opening in member 24. Obviously, the bindlng posts 11 and 12 serve the double function of conducting current to and from the coils 8 and at least in part supporting the electromagnet upon the casing.

In the appended claims the term loosely mounted is employed to designate a mounting other than a rigid mounting and may include a spring or other elastic mounting. Moreover, the term yieldingly mounted is employed to define a mounting which per mits movement of the mounted member and does not necessarily mean a spring-like mounting.

I claim:

1. Electrical apparatus comprising a magnet, a magnetic armature movably mounted with respect to the magnet so as to be attracted thereby, and means for mounting the magnet so that it may automatically adjust its position with respect to the armature.

2. Electrical apparatus comprising a. magnet, a magnetic armature mounted in such manner as to be attracted by the magnet and as to move along a definite path under the influence of the magnet, and means for loosely mounting the magnet so that it may automatically adjust its position with respect to the path of the arma-- such manner as to be attracted by the maghanging projections for mounting the magnet approximately in alinement with said path, the said head being adapted to fit loosely Within the said slot so that the magnet may be orientated accurately into alinement with the said path.

5. An electric horn comprising a casing having an open forward end, a diaphragm mounted on the open end of the casing, an electromagnet disposed within the casing so as to actuate the diaphragm, a member of insulating material fitting around the rearward end of the core of the electromagnet, and means extending through the said member and the rearward end of the easing for at least partially supporting the electromagnet within the casing.

6. An electric horn comprising 'a casing having an open forward end, a diaphragm mounted on the open end ofthe casing, an electromagnet disposed within the casing so as to actuate the diaphragm means, a member of insulating material fitting around the rearward end of the core of the electromagnet, and one or more binding posts extending through the said member and the rearward end of the casing for conducting current to and from the electromagnet and for at least partially positioning the electromagnet within the casing.

7. An electric horn comprising a casing having an open forward end, a diaphragm mounted on the open end of the casing, an electromagnet disposed within the casing so as to actuate the diaphragm means, means for mounting the electromagnet on the easing including a member extending centrally therefrom through an aperture in the closed end of the casing, a member of insulating material fitting around the rearward end of the electromagnet, and one or more binding posts extending through the said member and the closed end of the casing for conducting current to and from the electromagnet and for preventing rotation of the electromagnet about the central supporting dayof March, 1917.

' BUTLER AMES. 

